We describe the results of 43 bronchoscopic examinations carried out on 35 patients who were HIV positive. Of these, 13 were intravenous drug abusers, 13 were homosexual or bisexual, six were haemophiliacs, two were homosexual intravenous drug abusers and one was a heterosexual contact of a drug abuser. All underwent investigation because of respiratory symptoms. Aetiological diagnosis could not be made from physical examination, x-ray or routine laboratory tests but, was usually made using bronchoscopy and its associated investigations. Using these techniques, Pneumocystis carinii pneumonia was the commonest diagnosis (19 cases) followed by bacterial infection. Mycobacterial infection accounted for two cases and non-specific interstitial pneumonitis accounted for three. Kaposi's sarcoma was found in one instance and eight investigations were non-diagnostic.